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Not your average great-great grandfather, Fauja Singh has completed nine 26-mile (42-kilometer) marathons since taking up long-distance running just over a decade ago.

On Sunday, the 101-year-old Sikh finished his final competitive race in Hong Kong, putting an end to a sporting career that has raised thousands of dollars for charity and been an inspiration to many around the world.

Nicknamed "Turbaned Tornado" by fans for his distinctive traditional headwear, Singh said he began long-distance running in an attempt to lift the depression that engulfed him after he witnessed the death of his son.

"I suffered a tragic incident in my life, a traumatic experience; I took up running as a new focus in life. And then marathon running developed from there," he told CNN at a training session before Sunday's race.

He completed the 10-kilometer route that wound its way along Hong Kong's harborfront in one hour 32 minutes and 28 seconds -- four minutes faster than his time last year despite a small stumble.

Fauja Singh smiles after completing the 10-kilometer run during the 2013 Hong Kong Marathon on Sunday.

"Five or six kilometers into the race, I really decided to go for it," he said. "I had lots of power today because I was very happy. "

Singh moved to the UK from India following the death of his son and entered his first marathon in London in 2000 aged 89.

In 2011, Singh became the first centenarian on record to complete a marathon after finishing the Toronto Waterfront Marathon in 2011 in eight hours and 11 minutes and six seconds.

He was also a torchbearer for the 2012 Olympics and was featured in Adidas' "Impossible is nothing" advertising campaign.

"He's focused, determined and single minded ... he's never set out to break records," said his trainer Harmander Singh, who has been coaching him for 13 years.

Although the Hong Kong event was Singh's last competitive race, his coach said the centenarian will still run for pleasure.

"He's my best student, I would say, which is ironic because he's twice my age."

As he hangs up his running shoes, Singh told CNN he had no secret diet or training regimen. He attributed his success to a simple love of the sport.

"It's because of the happiness I get out of it. If something makes you happy, you'll do it well."